Comparison of clinical, microbiologic, and clinicopathologic findings in horses positive and negative for Clostridium difficile infection

Objective - To compare clinical, microbiologic, and clinicopathologic findings among horses infected with Clostridium difficile that had toxin A in their feces, horses with evidence of C difficile infection that were negative for toxin A in their feces, and horses with diarrhea that were negative for C difficile infection. Design - Cross-sectional study. Animals - 292 horses and foals with diarrhea. Procedures - Feces were submitted for microbial culture and tested for the C difficile antigen glutamate dehydrogenase and for toxin A with a commercial ELISA. Results - Horses with toxin A in their feces had higher band neutrophil count, rectal temperature, hospitalization time prior to the onset of diarrhea, and total hospitalization time than did horses without evidence of C difficile infection, and 32 of the 33 (97%) horses with toxin A in their feces had received antimicrobials prior to the onset of diarrhea. Horses with toxin A in their feces had a significantly higher mortality rate than did horses negative for toxin A in their feces. Sensitivity and specificity of the ELISA for detection of C difficile antigen were 93% and 88%, when assay results were compared with results of microbial culture following direct plating, and 66% and 93%, when assay results were compared with results of microbial culture following broth enrichment. Conclusions and Clinical Relevance - Results provided some evidence that horses positive for toxin A had more severe clinical disease than did horses with evidence of C difficile infection that were negative for toxin A and horses with diarrhea without evidence of C difficile infection.